Project Euler > Problem 146 > Investigating a Prime Pattern (Java Solution)

Problem:

The smallest positive integer n for which the numbers n2+1, n2+3, n2+7, n2+9, n2+13, and n2+27 are consecutive primes is 10. The sum of all such integers n below one-million is 1242490.

What is the sum of all such integers n below 150 million?


Solution:

5777

Code:
The solution may include methods that will be found here: Library.java .

public interface EulerSolution{

public String run();

}
/* 
* Solution to Project Euler problem 46
* By Nayuki Minase
*
* http://nayuki.eigenstate.org/page/project-euler-solutions
* https://github.com/nayuki/Project-Euler-solutions
*/


public final class p046 implements EulerSolution {

public static void main(String[] args) {
System.out.println(new p046().run());
}


public String run() {
for (int i = 2; ; i++) {
if (!satisfiesConjecture(i))
return Integer.toString(i);
}
}


private boolean satisfiesConjecture(int n) {
if (n % 2 == 0 || isPrime(n))
return true;

// Now n is an odd composite number
for (int i = 1; i * i * 2 <= n; i++) {
if (isPrime(n - i * i * 2))
return true;
}
return false;
}


private boolean[] isPrime = {};

private boolean isPrime(int n) {
if (n >= isPrime.length)
isPrime = Library.listPrimality(n * 2);
return isPrime[n];
}

}

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